Fuel injection valve

ABSTRACT

A fuel injector ( 1 ), particularly for the direct injection of fuel into the combustion chamber of a mixture-compressing internal combustion chamber having external ignition, includes a valve housing formed by a nozzle body ( 2 ) and a sealing ring ( 34 ) which seals the fuel injector ( 1 ) from a cylinder head ( 36 ) of the internal combustion engine. The sealing ring ( 34 ) has a convexly curved profile, two ends ( 35 ) of the sealing ring ( 34 ) axially overlapping one another in a stepped manner.

FIELD OF THE INVENTION

[0001] The present invention is based on a fuel injector of the type set forth in the main claim.

[0002] From DE 196 00 403 A1, for example, an electromagnetic fuel injector and an appropriate structure for its mounting are known which satisfy the requirements regarding the sealing effect, thermal resistance and pressure resistance for an internal combustion engine having direct fuel injection. Particular attention is paid in this context to sealing the area immediately adjacent to the cylinder where the electromagnetic fuel injector is mounted, as well as to a region more distant therefrom. As a result, according to the present invention, a first sealing section having a first sealing ring, which is configured as a wavy washer, is located close to the cylinder and between the fuel injector and the cylinder head. Moreover, a second sealing section having a second sealing ring, which is also configured as a wavy washer, is located further away from the cylinder than the first sealing section.

[0003] Disadvantageous in the fuel injector known from DE 196 00 403A1, in particular, is the high production complexity of the sealing rings. Furthermore, due to the refined materials, the production costs are high, for instance when the sealing rings are made from silver-plated INCONEL or also from Teflon-coated materials.

SUMMARY OF THE INVENTION

[0004] In contrast, the fuel injector according to the present invention, having the characterizing features of the main claim, has the advantage that a sealing ring formed at a variable radius of curvature may be manufactured inexpensively from a copper-tin alloy, may be used repeatedly and is easy to install.

[0005] Advantageous refinements of the fuel injector specified in the main claim are rendered possible by the measures given in the dependent claims.

[0006] It is particularly advantageous that the sealing ring has an overlap region which, due to a locking of the ends of the sealing ring into appropriate cut-outs, attains a compact and flexible form of the sealing ring.

[0007] Advantageously, the sealing ring may be rounded on the inside and outside, either at identical or different radii of curvature, with the result that an even thickness of the sealing ring may be obtained or a cross-section tapering toward the edges.

BRIEF DESCRIPTION OF THE DRAWING

[0008] Exemplary embodiments of the present invention are shown simplified in the drawing and elucidated in greater detail in the following description. The figures show:

[0009]FIG. 1 a schematic section through a first exemplary embodiment of a fuel injector configured according to the present invention, in an overall view;

[0010]FIG. 2 a schematic section, in the area II in FIG. 1, of the fuel injector configured according to the present invention;

[0011]FIG. 3 a schematic section, in the same area as in FIG. 2, from a second exemplary embodiment of a fuel injector configured according to the present invention; and

[0012]FIG. 4 a schematic view of a sealing ring according to FIG. 2 or FIG. 3.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0013] Before giving a more detailed description, based on FIGS. 2 through 4, of preferred exemplary embodiments of a fuel injector 1 according to the present invention, to provide a better understanding of the present invention, a fuel injector 1 shall first of all be explained briefly in terms of its essential components with reference to FIG. 1.

[0014] Fuel injector 1 is designed in the form of a fuel injector for fuel-injection systems of mixture-compressing internal combustion engines with externally supplied ignition. Fuel injector 1 is particularly suitable for the direct injection of fuel into a combustion chamber (not shown) of an internal combustion engine.

[0015] Fuel injector 1 is made up of a nozzle body 2 in which a valve needle 3 is positioned. Valve needle 3 is in operative connection with a valve-closure member 4 that cooperates with a valve-seat surface 6, arranged on a valve-seat member 5, to form a sealing seat. In the exemplary embodiment, fuel injector 1 is an inwardly opening fuel injector 1 which has a spray-discharge orifice 7.

[0016] Nozzle body 2 is sealed by a seal 8 from an external pole 9 of a magnetic coil 10, and by a sealing ring 34 from the cylinder head, not depicted further in FIG. 1, of an internal combustion engine. According to the present invention, sealing ring 34 is made from a convexly curved ring overlapping at two ends 35, from surface-profiled coiled stock, by stamping and rolling. A detailed description of sealing ring 34 may be gathered from the description of FIGS. 2 through 4.

[0017] Magnetic coil 10 is encapsulated in a coil housing 11 and wound on a coil brace 12, which abuts against an inner pole 13 at magnetic coil 10. Inner pole 13 and external pole 9 are separated from one another by a gap 26 and are braced on a connecting member 29. Magnetic coil 10 is energized via an electric line 19 by an electric current, which can be supplied via an electrical plug contact 17. A plastic coating 18, which may be extruded onto internal pole 13, encloses plug contact 17.

[0018] Valve needle 3 is guided in a valve-needle guide 14, which is disk-shaped. A paired adjustment disk 15 is used to adjust the (valve) lift. An armature 20 is on the other side of adjustment disk 15. It is connected by force-locking to valve needle 3 via a first flange 21, and valve needle 3 is connected to first flange 21 by a welded seem 22. Braced against first flange 21 is a return spring 23 which, in the present design of fuel injector 1, is prestressed by a sleeve 24.

[0019] On the discharge-side of armature 20 is a second flange 31 which is used as lower armature stop. It is connected via a welding seem 33 to valve needle 3 in force-locking manner. An elastic intermediate ring 32 is positioned between armature 20 and second flange 31 to damp armature bounce during closing of fuel injector 1.

[0020] Fuel channels 30 a through 30 c run through valve-needle guide 14, armature 20 and valve-seat member 5, conducting the fuel, supplied via a central fuel supply 16 and filtered by a filter element 25, to spray-discharge orifice 7. Fuel injector 1 is sealed from a distributor line (not shown further) by a seal 28.

[0021] In the rest state of fuel injector 1, return spring 23 acts upon first flange 21 at valve needle 3 contrary to its lift direction, in such a way that valve-closure member 4 is retained in sealing contact against valve seat 6. Armature 20 rests on intermediate ring 32, which is supported on second flange 31. When magnetic coil 10 is energized, it builds up a magnetic field which moves armature 20 in the lift direction against the spring tension of return spring 23. Armature 20 carries along first flange 21, which is welded to valve needle 3, and thus valve needle 3 in the lift direction as well. Valve closure member 4, being operatively connected to valve needle 3, lifts off from valve seat surface 6, and the fuel guided via fuel channels 30 a through 30 c to spray-discharge orifice 7 is sprayed off.

[0022] When the coil current is turned off, once the magnetic field has sufficiently decayed, armature 20 falls away from internal pole 13 due to the pressure of restoring spring 23 on first flange 21, whereupon valve needle 3 moves in a direction counter to the lift. As a result, valve closure member 4 comes to rest against valve-seat surface 6, and fuel injector 1 is closed. Armature 20 comes to rest against the armature stop formed by second flange 31. In a part-sectional view, FIG. 2 shows the section designated by II from FIG. 1 of fuel injector 1 designed in accordance with the present invention. Identical parts are provided with the same reference numerals in all of the figures.

[0023] To illustrate the functioning method of the measures for sealing according to the present invention, FIG. 2 schematically shows a part of cylinder head 36 of the internal combustion engine. Sealing ring 34 is positioned in a groove-type recess 40 of nozzle body 2 in such a way that it seals fuel injector 1 from cylinder head 36 of the internal combustion engine. In this context, sealing ring 34 is under a light pressure which slightly flattens the afore-mentioned convex radius of curvature of sealing ring 34, thereby producing the sealing effect. Sealing ring 34 is wedged in circumferential recess 40 by outside edges 41.

[0024] Sealing ring 34 preferably is manufactured by punching, from surface-profiled coiled stock, and subsequent rolling. Sealing ring 34 formed in this manner has two ends 35 which are positioned so as to axially overlap each other and to interlock in the circumferential direction. One possible form of overlap may be inferred from FIG. 4.

[0025] To ensure excellent elastic qualities of sealing ring 34, it is preferably manufactured from a copper-tin alloy or from stainless steel. The material also has good corrosion resistance and excellent sliding characteristics. The former is indispensable for a long service life of the sealing ring; the latter facilitates especially the installation and removal of fuel injector 1, without having to replace sealing ring 34 each time, as is the case with conventional Teflon seals.

[0026] The installation of sealing ring 34 requires no specialized tools since, due to the elastic qualities, it is easy to slide it on nozzle body 2 and then lock it in recess 40. This is rendered possible by the overlapping of ends 35 of sealing ring 34, which makes sealing ring 34 variable in diameter.

[0027] The first exemplary embodiment of sealing ring 34 designed in accordance with the present invention, as shown in FIG. 2, has an identical radius of curvature for an inner side 38 and an outer side 39 of sealing ring 34. This means that the material of sealing ring 34 has an even thickness throughout.

[0028] In contrast thereto, the second exemplary embodiment of a fuel injector 1 designed according to the present invention, shown in FIG. 3 in a schematic section, shows a variable thickness of sealing ring 34. In this case, the material thickness decreases toward edges 41 of sealing ring 34, due to a larger radius of curvature of inner side 38 relative to outer side 39. The resulting form is advantageous insofar as the contact surface in recess 40 is smaller than in the first exemplary embodiment and, on the one hand, the installation is easier and, on the other hand, the sealing effect is improved.

[0029]FIG. 4 shows a schematic view of a sealing ring 34 according to FIG. 2 or FIG. 3 in the region of the overlap of ends 35. In this case, sealing ring 34 is turned 90° compared to the views in FIGS. 2 and 3.

[0030] To facilitate the installation and also to improve the elastic qualities of sealing ring 34, and consequently enhance the sealing characteristics as well, sealing ring 34 is provided with an overlap region where ends 35 of sealing ring 34 interlock, as already mentioned before. In the present exemplary embodiment, the overlap is achieved by axial locking. For that purpose, during production of sealing ring 34, cut-outs 42 are punched out at its ends 35 which, for instance, halve the axial height of sealing ring 34. During rolling of sealing ring 34, one end 35 each is inserted into opposing cut-out 42, so that a stepped axial locking is achieved. In this manner, the benefit is derived of a constant material thickness, as compared to a complete overlapping of ends 35, which would be achieved by sliding them over one another. Depending on the diameter of receiving bore 37 of cylinder head 36, ends 35 of sealing ring 34, of variable size, interlock with one another, due to the circumferential length of cut-outs 42. In this manner, sealing rings 34 are insertable into variably sized receiving bores 37.

[0031] The present invention is not limited to the exemplary embodiments presented, but is applicable to other cross-sectional forms of sealing rings 34, as well as to various desired construction types of fuel injectors 1, such as fuel injectors 1 having an interface to an intake manifold or a common-rail system. 

What is claimed is:
 1. A fuel injector (1), especially for the direct injection of fuel into the combustion chamber of a mixture-compressing internal combustion chamber having external ignition, comprising a valve housing formed by a nozzle body (2), and a sealing ring (34) which seals the fuel injector (1) from a cylinder head (36) of the internal combustion engine, wherein the sealing ring (34) has a convexly curved profile, two ends (35) of the sealing ring (34) axially overlapping in a step-like manner.
 2. The fuel injector as recited in claim 1, wherein one end (35) each of the sealing ring (34) is able to be locked into a cut-out (42) at the other end (35).
 3. The fuel injector as recited in claim 1 or 2, wherein a radius of curvature of the sealing ring (34) corresponds to a bore radius of a bore (37) in the cylinder head (36).
 4. The fuel injector as recited in one of claims 1 through 3, wherein the sealing ring (34) is made of a copper-tin alloy.
 5. The fuel injector as recited in one of claims 1 through 4, wherein the sealing ring (34) is positioned in a groove-type cut-out (40) of the nozzle body (2).
 6. The fuel injector as recited in claim 5, wherein the sealing ring (34), by way of outer edges (41), rests in the cut-out (40).
 7. The fuel injector as recited in one of claims 1 through 6, wherein the sealing ring (34) has the same radius of curvature at an inner side (38) and an outer side (39).
 8. The fuel injector as recited in one of claims 1 through 6, wherein the sealing ring (34), at an inner side (38), has a larger radius of curvature than at an outer side (39). 